Call charging telephone exchange system



Dec. 22, 1 931. R. E. COLLIS CALLCHARGING TELEPHONE EXCHANGE SYSTEM Filed June 26, 1930 Sheets-Sheet 1 //vv/v rm R. E. GaLL/s 5 6? '6. Jvuld ATTORNEY R. E. COLLIS CALL CHARGING TELEPHONE EXCHANGE SYSTEM Dec. 22, 1931.

Filed June 26, 1930 8 Sheets-Sheet 2 n m w w ff. E. COLL/a BY A URNE Y Dec. 22, 1931. R. E. COLLIS 1,837,206

CALL CHARGING TELEPHONE EXCHANGE- SYSTEM Filed June 6, 1950 8 Sheets-Sheet 3 E //v VENTUR H. E COLL/8' BY Q 6.6M

A T TURNE Y Dec. 22, 1931. RE. COLLlS I CALL'CHARGING TELEPHONE EXCHANGE 'SYSTEI Filed'June 26, 1930 8 Sheets-Sheet 4 INVENTUR R. E. G'qLL/s BY 61/111449?- A TTOHNEY R. E. COLLIS CALL CHARGING TELEPHONE EXCHANGE SYSTEM Dec. 22, 1931.

Filed June 26, 1930 8 Sheets-Sheet 5 uvvavnm H. E COLL/s ATTORNEY Dec. 22, 1931. R. E. COLLIS CALL CHARGING TELEPHONE EXCHANGE SYSTEM Filed June 26, 1930 8 Sheets-Sheet 6 lNVENTUR H. E. COLL/s By Dec. 22, 1931. R. E. coLLls 1,837,206

CALL CHARGING TELEPHONE EXQHANGE "SYSTEM Filed June 25, 1930' a Sheets-Sheet '7 Mill!!! W s HI' I/Vl/ENTUH H. E. DOLL/s A T TDRNEY Dec. 22, 1931. R. E. COLLIS 1,837,206

CALL CHARGING TELEPHONE EXCHANGE SYSTEM Filed June 26, 1930 8 Sheets-Sheet 8 g f Y I g m s I udu- I g a 7a) 5: 1 s l I ll m M m m;

R%? ff,s aw/ A T TURNEY Patented Dec. 22 1931 UNITEDTSTAQEISV PATENT vo1=151c1a:

RAYMOND E. COLLIS, or EAST oaAivGE, NEW JERSEY, assIeNoa T BELL rELErrroNE rmaomroams, INCORPORATED, or YORK, N. Y., conrom'rrorr. or 'NEW,

YORK L l CALL GEARGING TELE HON EXCHANGE sYs'rEuf "application filed June 26,

This invention relates to a telephone ex-, change system and more particularly to a system in which a charge is automatically made for a completed call. The object of the as to more equitably recompense the operating company for the use of exchange equip and maintain and it is not equitableto the operating company to provide service to all points in the exchange area at the same basic rate. i

Where calls are handled on a manual basis,

the rate of charge may be very easily cared for by the operator who is able to require the calling subscriber to depositJthe required number of coins in his coin box before giving him a desired connector, or to cause the proper operation of the subscribers message register. However, where calls are established entirely by dial switching means, some provision must be made for automatically controlling the charging of the call in accordance withthe zone of the exchange into which the call has been extended by the calling subscriber.

subscriber shall be enabledto .hold an established connection indefinitely. In manual I, systems theoperator is'able to assess the charge in accordance with the number ofumt invention is the provision of means for controlling the call charglng in sucha manner cated oflices must bereached over longinteroflice trunks which are expensive to install Furthermore, it is not equitable to the op erating company that for a basic charge the 1930. Serial No. 463,945.

periods during which conversation is continued on any call. Where, however, callsare extended by means of a dial switching by way of example, provisionis made whereby the charges for overtime periods of conversation may be made in accordance with the zone mto which the call has been extended and on a difierent basis than the charges for the initial period of conversation, This.

accomplished by the provision'of a'timing switch individualto a line finder district se-' lector linkwhich is started upon the response of the called subscriber and advances through a cycle to measure the prescribedunit period for conversation, the unit period having; been chosen as that which would be.

to the calling subscribers message register, the number of register operations de ending upon the zone of the exchange into w ich the calling subscriber has extended the connec the timing switch sends during each cycle is controlled by two zone recording relays which are controlled by the district selector se-- quenceswitch and by-the register sender, the

sequence switch. assuming difierent positions dependent on the zone into whichthe call is extended. By the provision of two zone be controlled." j

' zoneiintowhich-the call has been extended or During the latter portion of the first or initial cycle of the timing switch the prescribed time for the initial period of conversation is counted. If the conversation continues after the timing switch has completed its initial cycle, for example, after the elapse of five minutes, the timing switch tests to see if the connected subscribers are still conversing and is then started upon a second cycle. At this time, however, the circuits of the timing-switch'are altered in'such a manner-that duringthe firstportion of "the second cycle the impulses which are transmitted to operate the calling subscribers message. register are. transmitted on a'fdifferent basis than for the initial period of conversation. In the modification of the invention chosen for illustration the message register operations for calls to zones 0, 1, 2, 3, 4 and 5 are none, one, two, three, four and five respectively for theinitial perio'd of conversation'; whereas for the overtime period of'conversation, the message register is not operatedlfor calls to zone 1, but is operated once for calls to the'zoth'er zones. By slight chan es in the wiring of the timing circuit the c arging'impulses may be varied at will to meet the trafiic requirements of the particular exchange in which the equipment :is installed.

As the timing switch advances throughthe latter part'of its second orovertime cycle, it measures theprescribed time for the overtime period of conversation; .This'overtime periodmay be varied in accordance with the may' bemade uniform for all calls. In the modification illustrated the overtime periods are varied inaccordance'with the zones and may, for example,for zones .0, 1, 2, 3, 4 and 5 bef'no limit, five minutes, three minutes, two minutes, two minutes and one minute'respe'ctively. If the conversation continues afterthe completion of the second cycle of the timing switch, the timing switch will advance through additional overtime cycles as long" as the conversation continues and will continue to operate the subs cribers' message register for each such cycle. I

"Inorder to guard against false charging an dnndertiming due to trouble crosses and trouble grounds in the timing circuit and in the line finder district selector link, safeguardshave been incorporated into the circuits which serve to prevent excessive charging-orundertiming of the periods of conversaton when a trouble condition arises. By this provision a subscriber always receives the full measureofservice to which he is entitled for the-charge-which is registered on his message register.

Aclearer conception of the scope and purpose of the' inventionwilhbe obtained from a 05 consideration of the following description in connection with the attached drawings in which:

Fig. 1 shows a calling subscribers line together with certain relays common to groups of calling lines.

to the'line'finder district selector'link circuit of Figs. 3 and .7 for controlling the calling subsc'ribers message register.

Fig. 8 shows inschematic form selectors for completing a connection to an automatic subscribers line, to a manual office or to an operators position.

'Fig.9'sl1ows the manner in which Figs. 1 to'8 should bearranged.

The invention has been embodied in a disclosure'whiclris similar to that of U. S. Patent 1,567,072 granted to W. H. Matthies December 29, 1925, both the present'disclosure and that of the Matthies patent showing a skeletonizedsender substantially the same as that disclosed in the more complete disclosure of U. S. Patent 1,589,402'granted to O. H. Kopp June 22, 19'26 andreference to the Kopp patent is made for operations notcompletely described herein.

As disclosed in the'above mentioned patents, a plurality of link circuits is arranged toserve'agroup of calling lines and are taken into service in rotation. When a link circuit completes its function it hunts for and associates itself with 'a district selector which is ready for use'and the link and district remain in a sub allotted condition until the next link in'the series has-been put into service. The link circuit is then put into an allotted condition from which it will be advanced by the initiation ofa call and-the action of the-start circuit of Fig. 2. The-trip circuit of Fig. 1 and start circuit of Fig. 2 are-so arranged that only one'line maybe served at a time and so that there may be cooperation between two groups/0f line's to each of which a group'of link circuits is individual. The details of these functions are described in the above mentioned Matthiesfpatent and since they form no partof the present'invention will be omitted fromthe following description.

Establiahv'nent 0 f 0; connect-2'0 It will be assumed that the subscriber at through the winding of relay 101, back con-Q tact of relay102over'the subscribers line to ground at theouter contact of relay 102. Belay 101 in operating closes a circuit from battery, Winding of relay 103, right back contact of relay 104, to ground at the outer front contact of relay 101. It also prepares a circuit from batterythrough resistance 111 and the left winding of marginal relay 109 in parallel, inner front contact of relay-101 to conductor 114 to identify the calling line to the line finder. Relay 103 in operating closes a circuit from battery over the back contact of relay 201, conductor 130 right wlndlng of relay 108, inner back contact ofrelay 107,

back contacts of relay 109, middle left conrelay 103. Relay 108 prepares a circuit from ground at its outer right front contact through the winding of trip magnet. 303 of the line finder to batter T in re aration for tripping the proper set of brushes when the line finder is operated. Relay 201 operates in the locking circuit of relay 108 and in combination therewith closes a circuit from ground over its outer right contact, conductor 128, inner right contact of relay 108, winding of relay 1.10, to battery. Relay 110 locks over its inner right contact, the lefthaek contact of relay-109 to ground at the middle left front contact of relay 103., Relay 110 closes a circuit for starting the allotted line finder,

Assuming that the. link and line finder shown are the ones to be used next, sequence switch 400 will be standing in positionl and sequence switch 700 in position 2. The operation of relay 110 will therefore close a circuit from ground atits outer right contact, outer left front contact of relay 108, inner left front contact of relay 103, conductor 131,

- left back contact of relay 202, inner left back contact of relay 203, conductor 206, upper left and lower right contacts of earn 403, brush 402 and terminal 401, conductor 378, lower contactsof cam 701, winding of relay 302 to battery.- a v Relay 302 upon operating closes a circuit from battery through the winding of up drive magnet 304 of theline finder, inner upper contact of relay 302, upper contacts of cam 702, upper front contact of relay 302,- conductor 300, lower left contact of cam 601, conductor 602, lower left contact of cam'703, to ground. Relay 302 also locksover its inner lower front contact, the lower contacts of cam 704,the back contact ofrelay 3 05,

commutator segment 306 to ground on brush 307. The line findermoves upwardly under the control of magnet 304 and since the trip magnet 303 is 0 rated the proper set of brushes is tripped As soon as commutator brush 308 engages segment 309 a circuit is closed thereover, conductor 626, the lower left and upper right contacts of cam 705, conductor 404, contact 230 of key 204, inner right front contact of relay 201 to conductor 129 and'the right windin g of relay 201. This circuit shunts the winding of relay 108 and causes that relay to release in turn releasing the trip magnet'303, When brush 308'leaves segment 309 the circuit of relay. 201 is opened and that relay also releases. When line finder brush 381 makes contact with terminal 380 which is connected over conductor 114 to battery, a circuit is completed over conductor 310, right contactsof cam 603, conductor 311,.

winding of relay 305, conductor 312, upper right contact of cam604, conductor 605, to ground over the left contacts of cam 706. Relay o05 operates in this circuit and closes a shunt around its winding from ground over commutator brush 307 and segment 306, front contact of relay 305, conductor 313, resistance 606, upper left and lower right contacts of cam 603, thence as traced through the winding of relay 305, to ground at the left contacts of cam 706. This'shunt circuit reduces the rearrest the hunting movement of the line finder and connects ground from the right contact of cam 707, upper left and lower right contacts of ca1n'708, conductor 338, lower back contactof relay 302, lower back contact of relay 316, resistance 317, brush 326, terminal 327, conductor 112 to battery through the winding of cutoff relay 102. Relay 102 thereuponoperates disconnecting the line relay fromtheca'lling line which upon releasing in turn releases relay 109. a v At the time relay 302 operated it closed a circuit from ground at the lower left contact of cam 703 over conductor 602, the lower left contact of cam 601, conductor 300, theiupper front contact of relay 302,?the upper right contact of cam702, the upper right contact ofcam 709, conductor 379, terminal 407 and brush'406of the link district finder 410, lower right. contact of cam 408,winding of relay 409, r'esistance411 to battery. Relay 409 open ates and closes a circuit from battery throughv terminals of the idle sender.

the winding of sequence switch magnet 400,

upper contact of cam 412, 'to ground at the outer left front contact of relay 409 advancmg the link sequence switch 400 to position -.2. Whenswitch 400 leaves position 1 relay 409 releases. In position 2 a circuit is closed from battery through the winding of relay 4 13, upper left and lower right contacts of cam 414, right back contact of relay 415, to

ground at the right contact of cam 416. Be-

lay 413 operates closing a circuit from battery through the left winding of relay 417, right front contact of relay 413 to ground at the left back contact of relay 415. Relay 417 ;in operating closes a circuit from battery through the winding of updrive magnet 418 of thesender finder 420, left contact of cam 479, outer right contact of relay 417 to ground at the left back contact of relay 409. The

;- sender finder moves upwardly under the conate when the test circuit is later closed. The

test circuit extends from brush 422 over the lower contacts of'cam 419, right back contact ofrelay 409, left winding of relay 415, upper right andlower left contacts of cam 421, middle windingof relay 415 to ground atthe left contact of relay 413. An idle sender is characterized by battery connected to conductor 502. When, therefore, brush 422 engages terminal 423 corresponding to the sender of Fig. 5 which is assumed to beidle, thetest circuit above traced 'is completed over terminal 423 to battery and relay 415 operates quickly. Relay 415 in operating closes a locking circuit for itself from battery through its right winding left contacts of cam 421 to ground at the left front contact of relay 415. It also opens the circuit of relay 417 whichreleases'to in turn release magnet 418 and bring the sender finder to rest on the The release of relay 417 in turn releases relay 413. With relay 413 released and relay 415 operated a circuit is closed from battery through the winding of sequence switch magnet 400, up-

per left contact of cam 476, contact 427 of jack 428, left back contact of relay 413, right front contact of relay 415 to ground at the right contact of cam-416, advancing sequence switch 400 to position 3.

When the link circuit advances into posi tion 2 for hunting for an idle sender a circuit is closed" for relay 318 ext-ending from battery through the upper winding of this relay,

, lower left contact of cam 710, upper right cmtactiof earn ,711, conductor 37 5, terminal 477 and brush 478 of district finder 410, to ground at the right contact of'cam 429. With relay 302 released and relay 318 energized a circuit is closed for advancing sequence switch 700 into position 3 which may be traced from battery through magnet 7 00, the lower right contact of cam 712, the lower front contact of relay 318, conductor 319, lower contact of cam 607, conductor 608, upper back contact of relay 302, conductor 300, the lower left contact of cam 601, conductor 602, to ground at the lower left contact of cam 703. As sequence switch 700 advances from position 2 to 3 relay 318 releases. With sequence switch 7 00 in position 3 busy ground is applied to'the sleeve conductor 115 over line find-er brush 326, resistance 317, lower back contact of relay 316 to ground at the lower left contact of cam 707.

When sequence switch 400 reaches position 3 a circuit is closed from ground through the left and middle windings of relay 503, back contacts of relay 504 and 505, conductor 506, terminal 430, brush 431, upper con tact of cam 434, brush 432, terminal 433, conductor 320, lower right and upper left contacts of cam 13, assuming that the district selector sequence switch 700 has now advanced to position 3, through the winding of relay 351 to battery, and in parallel over the lower left contact of cam 714 to battery throughthe upper winding of relay 316. Relay 316 is marginal and does not operate. Relay 351 operates but is ineffective at this time. Relay 503 also operates and closes an obvious'circuit for relay 507 which in turn closes a circuit for relay 509. Relay 509 closes a circuit for relay 510.

As soon as sequence switch 400 arrived in position 2% it prepared the pulsing, circuit for receiving dial pulses. This circuit may be traced frombattery through the left winding of relay 500, conductor 537, terminal 440, brush 441, lower contact of cam 429, brush 47 8,'terminal 477, conductor 375, lower contact of cam 715, upper back contact of relay 316, brush 334, terminal 333, conductor 117 through the subscribers substation, conductor 116, terminal 332, brush 331, inner lower back contact of relay 316, winding of relay 716, upper contact of cam 717, conductor 382, terminal 442, brush 443, upper right and lower left contacts of cam 403, brush 444 and terminal 445, to ground at the back contact of relay 513. Relay 500 operates in turn operating relay 518 in the well known manner, relay 518 in turn operating relay 519. A circuit is thereupon closed from the source of tone current 516 through the right winding of relay 500, switch 520 in its normal position, front contact of relay 519, contact ofcam 514 to groundat the front contact of relay 509. This tone is transmitted to the calling subscriber to inform him that the are 534 of-the translator. Withr'elay 547 sender is ready to receive impulses which he may then send by manipulating his dial.

When relay 510operated it removed battery from conductor 502, releasingrelay 415. With relay 415 released, a circuit is closed from battery through v the winding of sequence switch magnet 400, lower left contact of cam 476, right back contact of relay 415, to ground at the right contact of cam 4165; Sequence switch 400 advances to position 5 over this circuit and remains in this position throughout the further operation of the sender. V

The calling subscriber now proceeds to dial the desired'line numberfor setting the registers and translator (not shown) of the sender in the well known manner. After dialing the first digit the switch one wiper of which is shown at 520 advances from normal closin a circuit extendingvfrom battery through tie winding of relay 517, terminals and wiper 520, contacts of relay 519, contact of cam 514,

to ground at the outer right contacts of relay 509. Relay 517 closes an obvious circuit for relay 521. A r

As soon as thecode registers of the sender have been set in accordance with the first two digits dialed by the calling subscriber,

the translatoris set'in a manner described in the aforementioned patent to "0. H; Kopp; When the translator .assurnesits setting, Ielay 533. operates and circuits are prepared over the translator arc 534 through aback contact of relay 535 for operating eitherrelay 536 or relay 547 or neither of them de- 'contact of cam 711, conductor 378, terminal pendent upon in which zone of the exchange the wanted line is located. "For example, if a called number is dialed for either zone 0 or zone 1, neither relay 536 or 547 willbe operated. Ifa call is dialed for either'zone 2 or zone3, relay 536 will be operated and if the call is for either zone 4 or zone '5, relay 547 will be operated. It will be assumed that a call is for a subscribers line terminating in the fifth zone and that therefore relay 547 is operated over a circuit extending from battery, winding of relay 547, back contact of relay 535, translator arc534 to ground at the contact of relay 533. Relay 547 locks over its left front contact, the contact of cam 514 to ground at the outer right frontcontact of relay 509 and extends its locking ground to the windingof relay 538. Relay 538 upon operating establishes a circuit from ground at theouterright contact of relay 509over the contact of cam 514, the contact of relay 538 to battery through the winding of relay 535.

Relay 535 operates opening thezinitial energizing circuit of relay 547 andconnecting the translator are 534 over a cable 539 to the class switch 540, which is. diagrammatically indicated in the upperrig'ht portion of Fig. 5. The class switch is thereupon set from the operated and relay 536 non-operated,a-circuit iswprepared extending 7 from battery -,through low resistance 549, right front contact of relay 547, rightback contact of relay. 536, the contacts of cams 541 and 542,.these cams being closed: during'the district brush selection positions of the sequenceswitches associated with the sender, conductor 543, terminal 439, brush 438, right contacts ofcam 405, brush 406,- terminal 407, conductor. 379 to the upper right contact of cam 709. a This circuit is completed as will be described here- .inafter when the district sequence switch is Ladvanced to position- 4% through the left windings of zone relays 609 and 610 of the registration controlling circuit of Fig. 6 for.

indicating the fact that the subscriber has directedthe call to a particular zone of the exchange, in the case assumed, the fifth zone. It may be'noted at this time thatidue to the inclusion of the low resistance 549 both zone relays 609 and 610 will operate. Had'relay onlyrelay-610 would then be operated as soon as'thedistrict sequence switch'reaches position 4%. If neither relay 536 or 547 operate then direct ground is connected to t e circuit prepared through the windings of rellays 609 and 610 and neither-of the latter relays will operate. With sequenceswitch 700 in position 3 relay-318 is energized over a circuit extending.

from battery through its upper winding, the lower left contact of cam 710, the lower left 401 and brush 402 of district finder 410, the upper contacts of-cam 435, brush 436 and terminal- 437 of sender finder 420, the contact of relay' 521, the back contact of relay 504,: the right contact'of cam 526, winding of "sender stepping relay 522, back contact of relay 525, left winding of overflow relay 523, left contact of cam 527,fresistance 530 to ground. Relays 522 and 318 operate: in this' closes a circuit to advance sequence switch 7 00 into position 4 extending from battery through the winding of magnet700, lower right contact of cam 712, lower'front con tact'of relay 318, thence as previously traced toground at the left contact of cam 703.

The district selector is now controlled by the sender in its brushandngroupselection movements and then proceeds to hunt for an idle trunk in the wellknown manner. When the district sequenceswitch reaches position 4% after the completion of brush selection,

the circuitpreviously traced from the contact of relay 547 andextending to the upper right contactofcam 709 is extended over the lower left contact of cam 709, conductor 611 to ground: through the leftwindings of zone relays 610 and 609. Relay 609 and; relayx6l0 *operate. and lock over their'right windings and inner right front contacts,.conductor 612 toground atthelower left contact of cam 707.

After an idle trunkis selected a circuit is established inpositi'on 9-of sequence switch700 j for relay 318 extendingfrombattery through 318 upon operating advances sequence switch 700 1 into position. 10*: over a. circuit extending from ground; on. the lower front contact of relay. 318, lowerrright contact of cam 712 to battery through-the winding of magnet: 700. In position 10relay 318 remains energized over thecircuit previously traced: vIn position .10, whichisatheselectionbeyondposition ofthe district" selector sequence. switch, the

. control of succeedingiswitches is effected over a fundamental circuit? which. may be traced in. part from. brush 7.21,,the upper right. and

lower left" contacts of cam;722, conductor-:7 23, the lowerv back, contact of relay 321', conductor 378, thence as traced to-the sender through 3o thewindi ngsrof'relays522 and523,;cam-5q46,

brush 544 and compensating-'msistance 545,

'the back contact of relay 524,.theright-f'ront contact-ofrelay 50.7., conductor 543', terminal Y 439 a-ndi brush 438, .the' right contacts. of cam 1405', brush, 406,.terminal 407;,conductor. 379,

the upper left and: lower right contacts of cam 724' to brush725. 1 1

As soon-as the selections are completed and the connection has been. set: up: to .the called subscribers line 800,.' reversed. battery from theincoming selector 801 operatesrelays-v 522 and 523m the usual. manner. These relays, inturn, cause theoperationzof relay 531 and relays 52413.11 504. With theserelays operatedthesendersequence switch-is advanced windingimthe circuitof relays351 and 316.

' Relay 351 thereupon releases, in,turn-,,opening the-.circuitsofi relay 318, which also releases. Upon.therelease-of relay318 thedistrictsequence switch-700 is advanced into vpositionll over a circuit extending from battery, winding of magnet? 700, 7 right contacts of.-'cam.726, lower hack-contact of relay 318,

to ground astraced-at the lower left contact.

of cum 703. As the'sequence switch enters position 11, ground'is connected 'to conductor 320 at the lower left contact of cam 720 over terminal 433, brush: 432, upper, contacts of cam 446, left windingofrelay-4'15, rightback contact of relay. 409, lower contact of cam 434, brush 431, terminal 430, conductor 506, left backcontact of relay 505, windings of relay 503; Since these windings are also connected 'to ground relay 503 now releases, in turn releasing relay 507. The release of relay 507 does not release relay 509, sincethat relay is locked to its own front contact. A circuit istherefore closed from ground over the left back contact of relay 507, front contact; of relay 509 to the winding'of relay 505, which relay locks over its middle left contact to conductor 506 and to ground as above traced. Afterleavingposition 10 relays 351 and 3.16 are both disconnected from conduc tor 320'. Sequence switch 7 00 is then advanced-into position 12 over a'circuit extending from battery through magnet 700, the lowerright contact of cam 712, the left contacts of cam 708 to ground at the right contactc-f cam'707. In passing into position 12 the subscribers line becomes disconnected from the sender at contactsof cams 715 and 717.

Talking selection With sequence switch 700 in position 12 relay. 318 isenergized in acircuit extending to thesender from battery through its upper winding, thelower left contactof cam 710, the lower left contact" of cam 711, conductor 37,8, terminal 401, brush, 402,.upper contacts of, cam 435, brush 436, terminal 437, conductor 532, the front, contact of relay. 521, the front contact of relay 504,.the right contact of cam 52.6, the sender. sequence switch being in position18 fortalking selection, the windings of relays 522 and 523, the right contactof cam 527, the right back contact of relay 507 togroundthrough. resistance 530. Relays 318 and.522energize in this circuit, relay 318 closing a circuit extending frombattery. through sequence switch magnet 700, the lower right contact of cam 712, the lower front contact ofrelay 31,8, conductor 319, right contacts of cam 607 ,.to ground at the lower right contact of cam 703. Relay 318 upon energizing locks to the fundamental circuit over its upper winding and outer upper front contact and the lower right contact of cam 710.. As sequence switch 700 rotates outof'position 12,toward position 16, ground isintermittently connected to the fundamental circuit in shunt of sender stepping relay 522 at the upper right and lower left contacts of cam 706. lVhen the sender is satisfied as to its talking selection se.t ting,-the, fundamental circuit is opened at the sender through the operation of relay 525 and relay 318 deenergizes arresting the sequence switch700 in its next stopping posi tion. The sequence switchmay be arrested in anyone of three positions, position 13 which is a charging position for connections to zones, 0,2 and: 4, position 14 whichis a to ground. -Relay 409 looks through its inner Vground at the outer left front contact of switch magnet 400, lower right contact of cam 476, right back contact of relay 417 to ground charging position forvconnections to zones "1, 3 and 5 and position 15 for connections to an operators position. Since it has been assumed that the calling subscriber has made a call into zone 5 for the'exchange, the district sequence switch will be arrested in talking selection position 14. v a I At the sender after talking selection is completed relay 515 operates connecting bat tery to conductor 506 in parallel with the, winding of relay 505. The current-gin this circuit is now suflicient to operate relay 415 which closes a circuit from battery through the left winding of relay 417, lower contacts of cam 421 to round at the left front contact of relay 415. elay 417 closes a circuit from battery through the winding of sequence switch magnet 400, upper contact of cam 47 9, outer right front contact of relay417, left, back contact of relay 409 to ground, advancing sequence switch 400to position 6. In this position all of the conductors extending to the sender are opened and the sender is completely released. *As soon as sequence switch 400 leaves position 5,'relay 415 releases and, in turn,"releases relay 417, unless the sender finder 420 is standing on one of its top ten terminals. If the latter condition exists relay 417 is held operated in a circuit from battery over its left winding, left front contact,upper' contact of cam 424, commutator segment 464, brush 463 to ground With relay 417 operated at this time acircuit is closed from battery through resistance 411, winding of relay 409, upper right and lower left'contacts of cam; 414, inner right front contact of relay 417, right-contact of cam 416 left contacts to ground at the upper contact of cam 467 and alsocloses a second locking" circuit for relay 417. With relay 409 operated a circuit is closed from battery through the winding of down drive magnet 465 of the sender finder 420, left contact of cam 412 to relay 409. When the sender finder reaches its lowermost position a circuit is closed from ground over brush 463, bottom commutator segment 406, upper contact of cam .456 to resistance 411, shunting the winding of relay 409 and causing that relay to release and, in turn, release relay 417. With relay 417 released in position 6, a circuit isclosed from battery through ,the winding of sequence at the right contact of'cam 416, advancing sequence switch 400 to position When sequence switch 400 reaches position 7, the link circuit is ready to associate itself with another district selector. ,If another district selector is standing in position 1 0 Contact of cam 720 of that district selector,

lower-right contact of cam 713, upper right contact of cam .714, contact 727 of jack 728, conductor 392, contact of jack 448, contact of jack 449, upper left contactof cam 416, right back contact of relay 415, lower right and upper left contacts ofcam 414, winding of relay 413 to battery. Relay 413 closes a circuit from battery through the left winding of V V relay 417, left 7, front contact of relay 413 to ground'at the left back contact of relay 415.

'Relay 417 in operating closes a circuit for uplector, contacts 730 of jack 728to conductor 366. Relay 413, in operating, closes the same "circuit through the right and'middle windings of relay 415 as it closed in position 2. 1

At this time the test circuit'extends from around at the left front contact of relay 413 through the middle winding of relay 415,

lower left and upper rightcontacts-of cam 421, left winding of relay 415, rightback contact of relay 409,lower right and upper left contacts of relay 419, contact of jack 449 to brush 451, V q a y If the district selector for which the district selectorfifinderf is hunting does not lie between the lastposition occupied by the finder and the top oftits bank, it .will continue to move upwardly until brush 4553 engages segment 452 completing a circuit'over theupper right contact of cam 408, winding of relay 409. resistance 411 to'battery. The operation'of relay 409 opens the test; circuit,

1 opens the circuit of updrive magnet'447 and closes a circuit from battery through the -wind ng of downdrive magnet 454, lower "right contact of cam 41,2,"left frontv contact of relay 409 to ground. The district selector finder is restored to its lower-most position under the control of magnet 454 at which time a circuit is closed from ground over brush 453, bottom segment455 of the dis trict selector finder commutator, lower right contact of cam 456 to resistance 411, shunting and relea sing relay 409 which restores the test circuituand the circuit of updrive .inagnet 447; 'VVhen brush 451 encounters terminal towhich conductor 366 extends, the 7 test circuit is completed and relay 415 operates quickly as in the previous case. Relay 415 locks through right winding, the left contacts of cam 421 to ground at its leftlfl'ont contact'opening the circuit of relay 417 to deenergize magnet 447 and bring the district selector finder to rest on'the terminals of the district selector. With relay 415'operated and relay 417 released, a circuit is 'closedjfrom battery throughlthe winding of sequence switchmagnet 400, upper left contactofi cam 476," contact'427'of ack 428, back'contactof relay 413, right front contact of relay 415, upper left contact of cam 416,

contacts 'of' jacks 449 and 448' to conductor 392; Sequence switch 400 advances to position 8 in this circuit.

Relay 4'15 is heldoperated in position 8' from battery atthe district selector over terminal 450, brush 451, contacts of jack 449, upper left and lower right contacts of cam 419, back. contact of relay 409, left'winding of: relay 415', upper right and lower left contacts of cam 421'to ground at the left front right contact of cam 712, lower front contact of relay 318,-thence as traced to ground at the lower left contact of camp 703; Sequence switch 700 advances to position 2,

releasing relay 318. The advance to posi- "tion.2 removes ground from conductor 392 and battery from conductor 366. The removal of'battery from conductor 366 opens the circuit ofrela-y 415 and that relay releases, closing a circuit from battery through the winding-of sequence switch magnet 400, lower left contact of'relay 476, right back contact of relay 415 to ground at" the right contact ofcam 416. Sequence switch 400 ad vances-to-position 9;

The link. circuit remains in this position until the link standing next to it in the series is advanced from position 1 for the purpose of selecting a: sender. Link circuit 260 occopying that relationship to thelink circuit of Fig. 4, a circuit may be traced from ground over the lower contact of cam 261', upper left contact of cam 262, conductor 263, contact 460 of jack 428, upper right contact of cam 461, lower right contact of cam 462, winding ofrequence switch magnet 400 to battery, advancing the link circuit sequence: switch to position 10 which is the equivalent of position 1 so that the link circuit is ready to operate in responseto the next call in the group of lines served thereby.

Returning to-the operation of the district selector in the establishment of" the connection, as soon as the sequence switch 700 advanccs into the talking position 14 a circuit 7 is established forsupplying the calling subscriber with talking current, which circuit maybe tracedfrom batterythrough the lower left-winding-of repeating coil: 731, right contaoti of. 08!]1211'7', winding'of relay-716, inner lower back contact of relay 316, brush 331 and terminal 332, conductor 116 overthe subscribers line, conductor117, terminal 333 and .brush334, upper back contact of relay 316,

upper right contact ofca'ni 715 to ground [liaising emit 5a.? chavy e for (1 call into zone 5 of the exchange area It will he recalled that for a call into zone 5.

of the exchange area the district sequence switch 700 was arrestedin talking selection position 14 and that both zone relays 609 and 610 have been oeprated and locked. hen the called subscriber 800 responds after the application of ringing current to his line from the incoming selector 801 in the well known manner, relay 301 operates in a circuit which may be traced in part from brush 721 over the upper contacts of cam 722, the upper right winding of repeating coil 7 21, the lower right and upper left contacts of cam 733, the winding of polarized relay 301, the lower right winding ofcoil 7 31, the lower contacts of cam 724 to brush 7 Upon operating, relay 301 establishes a circuit extending from battery through the winding of relay 302, the lower contact of interrupter 322, as soon as the interrupter advances, conductor 323, the lower contact of cam 613, conductor 614, the lower contacts of cam 718, conductor 734, the front contact of relay 301 to ground at the'upper left contact of cam 703. Relay 302 then locks over its lower front contact, conductor324, the upper right and lower left contacts of cam 615, conductor 616, the lower right contact of cam 719, the lower right contact of cam 718, conductor 734, front contact of relay 301, thence to ground as previously traced. When the upper contact of interrupter 322 closes acircuit is established from ground at the upper left contact of came 703 thence as traced to interrupter 322, over the upper front contact of relay 302.

the right contacts of cam 7 02, the lower contacts of cam 705, conductor 735, the lower left contact of cam 617 to battery through the winding of sequence switch magnet 600 for advancing this sequence switch into position 2.

With sequence switch 600 in position 2 a circuit is established extending from batterf. through the winding of relay 321, conductor 325, upper left contact of cam 613,

conductor 614. the lower left contact of cam 718, the lower right contact of cam 7 19, con duct-or 616 to ground over the left contacts of cam 615. Relay 321, upon operating,

lO-ClTS over its inner upper front contact to g nd. at the lower right contact of cam 703. When sequence switch 600 leaves position 1, the holding circuit of relay 302 is opened at the contacts of cam 615 and relay 302 releases. Switch 600 is advanced through positions 2 to 6 into position 7 under the control of interrupter 618 in the following man-y ner: When sequence switch 600 reaches position 2 a circuit is established from ground over the upper contact of cam 619, the lower contact of interrupter618, upper right and lower left contacts of cam 620, right back contact of relay 621, conductor 312,:winding of relay 305, conductor 311,lo wer contacts'of cam 603, conductor622 to battery... Relay 305 operates and prepares a holding circuit for itself extending from battery over the circuit preyiously traced, through the winding of relay 305, conductor 312, the lower contact of cam 604:, the winding of relay 621, conductor 313, the front contact of relay'305 to ground over the line finder commutator segment 306 and brush 307. Relay 621 does not operate in this circuit until the interrupter 618 opens its lower contact. When relay 621 operates a circuit is established from battery through resistance 623, lower right contact of cam 624, lower right contact of cam 625, conductor 626, lowercontacts. of cam 705, conductor .735, the lower contacts of cam 627, the right front contact of relay 621, conductor 310 to brush 381, terminai 380, conductor 114', back contact of line relay 101 to ground through the calling sub-'- scribers message register 105. The message j register is thus operated once to register a charge. Relay 621 at its right back contact also opens the circuit previously traced to the lower contact of interrupter 618.

As soon thereafter as [interrupter 618 closes its upper contact a circuit is established from ground at the upper contact of cam 619, upper contact of interrupter 618, inner left front contact of relay 621 to battery through the winding of sequence switch imagnet 600 for advancing the sequence switch to position 3. When the sequence switch leaves position 2, relays 305 and 621" whereupon relays305 and 621again release. In position 6 the previouslytraced clrcults release, their holding circuit bein'gopened at the lower left contact of cam 603; Relay 621, upon releasing, opens the circuit of sequence switch magnet 600 to arrest the sequence switch in'position 3. In position- 3,

sender, right contacts of cam 627, right front contact of relay 621, conductor 310 and thence as traced to ground through the message reg-.

ister magnet 105. The message register is thusoperated a second time. As soon thereafter as interrupt-er 618. closes its upper contact'the previously traced circuit is closed for advancing sequencev switch 600to position l, whereupon relays 305 and 621 again release. In position 4 thepreviously' traced circuits are established under the control of the lower contact of interrupter 618 for reoperating relays 305 and 621. W ith;

sequence switch 600 in position 4 and relay 621 operated, the circuit of message registry 105 is through resistance 623, the lower. right and upper left contacts of cam 624,,thenceas previously traced throughthe inner left front contact of relay 610 to ground through the message register magnet 105. ,The message register is thus operated a third time.

WVhen the interrupter 618 again closes its upper contact thesequence switch 600 is ad vanced to position 5, aspreviously described, whereupon relays 305 and 621 again release.

In position 5 thepreviously traced circuits areestablished under the control of the lower contact of interrupter 618 forreoperating relays 305 and 621. .With sequence switch 600 in position 5 and relay 621 operated the circuit of messageregister 105 is again es tablished from battery, through resistance 623, the lower right contact of cam 624, the lower left contact of cam 629, the left front contact of'zone relay 609, the upperleft contact of cam 607, conductor 608, upper back contact of relay 302, conductor 300, upper contact of cam 601, inner left front contact of relay 610, right contacts of cam 627, right front contact of relay 621, conductor 310 and thence as traced to ground through the messahe re ister ma net 105. The messa e re ist-er is thus operated a fourth time.

I When the interrupter 618 again closes its upper contact the sequence switch 600 is advanced toposition 6, as previously described,

areestablished under the control of the lower contact of interrupter 618 for reoperat ng reagain established from battery,

lays 305 and 621. With sequence switch600 in position 6 and relay 621 operated, the same was closed with sequence switch 600 in posififth time. When the interrupter 618 again closes its upper contact, the sequencewswitch 600 is advanced into position 7 and relays Inthe preceding description it has been assumed that the call was for a subscribers line circuit for message register 105iselosed as tion 5 and the message register is operated a r terminating in zone 5 of the exchange area. At this point the description of the progress of such a call will be arrested to describe how calls to other zones of the exchange area are charged for. It will be recalled that in the operation of the sender, relay 536 operated alone for calls to certain zones, relay 54k? operated alone for calls to other zones and that neither of these relays operated for calls to other zones and that with relay 536 operated the zone relay 610 of the register control circuit was operated and locl'ed, that with relay 547 operated both zone relays 609 and 610 operated and locked and that with neither relay 536 or 5 17 operated neither zone relay (09 or 610 operated. Further, it will be recalled that for calls to zones 0, 2 and 4, the district sequence switch 700 was set into talking position 13 and that for calls to zones 1, 3 and 5, sequence switch 7 00 was set into position 14%. g If, therefore, a local call is made terminating in zone 0 for which no charge should be made neither of zone relays 609 and 610 will be operated and sequence switch 700 will be set into talking position 13. Under this con' dition sequence switch 600 will not advance out of position 1 as the circuit previously traced for advancing it will be opened at the lower right contact of cam 705. In this case, relay 321 is operated following the operation of relay 302 over a circuit extending from battery, through its winding, conductor 325, the left back contact of relay 610, conductor 638, the left contacts of cam 705, the right contacts cream 702, the upper front contact of relay 302, the upper contact of inte *rupter 322, conductor 323, the lower contact of cam 613,'conductor 614, the lower contacts of cam 718, conductor 734, the front contact of relay 301 to ground at the upper left contact of cam 703. A locking circuit for relay 302 is now established through the winding of relay 302 and its lower front contact, the upper front contact of relay 321 to ground at the upper left contact of cam 7 20. Since sequence switch 600 is not advanced out of position 1, the message register 105 will not be operated. Hadfthe subscriber made a call into zone 1 neither of the zone relays 609 or 610 would be operated and sequence switch 700 would be positioned in talking selection position 142.. In charging position 2 of sequence switch 600, the circuit previously traced for operating the message register 105 would be closed at the lower contacts of cam 705. 'However, as the sequence switch 600 passed through charging positions 3 to 6, inclusive, due to the unopen ated condition of zone relays 609 and 610 no operating circuits for the mess-a register 105 would be closed and therefore 1 1e message register would be operated but once,

Had the subscriber made a call into zone 2, zone relay 610 would have operated and sequence switch 700 would. have been set into position 13. lVhen, therefore, sequ enc ister would not have been closed since the lower right contact of cam 705 would be opened. In passing charging positions 3 and l the circuits previously traced extending through the inner left front contact of zone relay 610 would be closed but the circuits previously traced in positions 5 and 6 of sequence switch 600 would be opened at the left contact of zone relay 603. Thus, for calls to zone 2 the message register 105 would be operated but twice.

l-lad the subscriber made a call in thezone 3,'zone relay 610 would have operated and sequence switch 700 would have been set in position 14. When, therefore, sequence switch 600 passed through positions 2, 3 and 4-, the previously traced circuits for operating the message register would have been established, but the circuits t seed in positions 5 and 6 of sequence switch 600 would have been opened at the left contact of zone relay 609. Thus, for calls to zone 3 the message register 105 would be operated three times.

If a call had been made into zone 4-, both zone relays 609 and 610 would have been operated and sequence switch 700 set int position 13. VJ hen therefore sequence switch 600 passed through charging positions 2 to 6 the circuits previously traced in connection with a call into zone 5 would have been established with the exception of the circuit established in position 2 of sequence switch 600 which will be opened at the lower right contact of cam 705. The message register 105 would thus be operated four times for calls to zone 1.

Timing the z'u-izfe'al period 0 f cmwersatz'on for calls to zone 5 Returning to the consideration of the call which it was assumed, the calling subscriber had made to subscribers line 800 terminating in zone 5, it will be recalled that following the registration of the call, the sequence switch 600 advanced into position 7 and relays 305 and 621 released. With sequence switch 600 in position 7 a circuit is closed from the office timing circuit 630 over the left contacts of cam 620, the right back contact of relay 621, conductor 312, winding of relay 305, conductor 311, the lower contacts of cam 603, conductor 622 to battery, operating relay 305; Relay 305 locks as previously described in with relay 621, relay 621 operating in the locking circuit of relay 305 as soon as ground is removed at the timing circuit 630. Relay 621 upon operating closes a ciriit from battery through the winding of sequence switch magnet 600, inner left contact of relay 621, lower left contact of cam 631 to ground at the lower left contact of cam 632, thus advancing the sequence switch 600 out of position 7. Upon leaving position 7 the holding circuit of relays 621 and30 5 is opened at the lower left contactof earn" 603,

and these relays release, relay 621 opening the circuit of magnet 600 to arrest the sequence switch'in position 8. Sequence switch 600 is thus advanced from position to position into position'18at30 second intervals under the control of timing circuit 630,"rneasnring off ten complete intervalsor a'rnaxi mum of 5 minutes for the conversation. r

As sequence switch 600 passes through position 16 a circuit is closed for relay 302 eX-' initial period of tending from battery, windingof relay302,

lower contact of interrupter 322, conductor 323, the lower contact of cam 613, conductor 61%, the lower left contact of cam 718, the lower rightflcontact of Camus), conductor 616, the lower left andiupper rightcontacts of cam 615, conductor,324E,-the upper front contact of relay 321 to ground atthe. upper left contact'of ca-m 720. Relay 302, upon operating lOClIS oyer its lower front contact to ground over the upper front contact of relay 321 independent of interrupter and of sequence switch 600. With sequence switch 600 in position 18 a check is made to detertacts of cam 718, conducton73 l, the frontv contact of relay 301 to ground at theupper left contact of cam 703. Relay 621, upon opera-ting, establishes a circuitfor advancing:

sequence switcht600 into position 1 which may be traced from battery, winding of magnet 600, the upper left contact of cam 62S, the outer left front contact of relay 621,

conductor 633, the middle upper front contact of relay 302,.conduct0r 634patched to the outer front contact of relay 610, armature of relay 610 patched to conductor 636, or over conductor 63a patched over conductor 639 to conductor 636, the lower right contact ofca-m 631, the lower rightcontact of cam 632, the outer left front contactof relay 621, con;

ductor 637, the front contact of relay 7161 0.

ground at the lowerleft contact ofcanr'i 20. l fith' sequence sw tch 600 in posit-ion 1 relay releases.

As soon thereafter as interrupter 322 closes its upper contact a circuit; is established for acvancing sequence switch 600 into position 2 which may be traced from battery, winding conductor 735, the low-er contacts of cam the right contacts of cam 702, the )er front contact of relay 302, the

1 5. per contact of interrupter 322 conductor .3, the lower'jcontact of earn 613, conductor magnet 600,lower left contacts of cam 614, thelower contacts of cam718, conductor 7 34, the front contact of relay 301 to ground at theupperleft contact of cam In p0si- 'tion 2 of sequence switch 600 the charging circuit is again established'for message register105 under the control of relays 305 and 621, as previously described, and sequence switch 600is advanced to'position 3 releasing relays 305 and 621'. With sequence switch 600 inl-position13 a circuit is established for advancing it to position 7 extending from bat tery through the winding of magnet 600, the upper right contact of earn 617, the outer right frontcon'tact of relay 610, con'ductor 63 middleupper front contact of relay 302, conductor 633, upper right contactof cam 631 to ground 7 at the lower left contact of cam" 632. lnfposition a circuit is established for advancing sequenceswitch 600 into position 8 extending from battery, winding of magnet 600, lower right c'ontact of cam 617, conductor 633, middleupper front contact of relay 302, conductor 634, outer right front contact of relay 610, conductor 636, lower right contact of cam 631 to ground at the lower left contact of cam 632. From position'S sequence switch 600 is driven directly into position 12, overa circuit extendingfroin battery through the winding of magnet 600, lower right contact of cam 617, conductor 633. middle upper front contact of relay 302, conductor 63%, the outer right front contact of relay 610, upper right contact'ofcam 624, lower left contact of cam 625,,i nner left front contact of relay 610, upper right contact of cam 635 to groundat the lower left contact of cam 632. From position 12 sequence switch 600 is advanced'into positi'on l l over a circuit which extends as previously traced from battery throu gh the wind ing of magnet 600 to the upper rightcontact 1 of cam 624, thence over the lower left con tact of ca m 625, inner left front contact of relay 610,;upperright and lower left contactsof earn 627, conductor 735, lower contacts of cam 705, conductor 626, lower contact of earn 635 to ground at thelower left contact ofcam 632.; From position "14: sequence switch 600 is advanced to position 16 over the circuit'previously traced to the upperleft contact of cam 625,'thence over the left front 3 contact of relay 609, the upper left contact of cam 635 to ground at the lower left contact of carn'632." With sequence switch 600 inposition 16 a circuit is established for relay" 305 from ground at the oihcetirningcircuit 630, over the left contacts of cam 620, the right bacl-z contact of relay 621, conductor 312, winding of relay 305, conductor 31.1,, the lower contacts of cam 603, conductor 622 to batteryoperating relay 305. Relay 305 looks as previously described in series with relay 6211, relay 621 operating in the locking circuitof relay 305 assoon as groundisremoved at the timing the lower left contact of cam 603' and theserelays release, relay 621 opening the circuit of magnet 600 to arrest the sequence switch in position 17. In the same manner sequence switch is advanced into position 18. The sequence switch in advancing from positions 16 to 18 under the control of the timing'circuit 630 has measured twothirtysecondintervals or a full minute for the overtime period for conversation.

In position 18- a check is againmade to determine if the conversation is still continuing and if so switch 600 is advanced in another revolution to charge and measure time in themanner just described for an additional minute of conversation. Additional overtime periods for conversation are measured and charged in this manner until disconnection occurs.

Charging (and timing overtime p67'i06l8lf07 calls to zones 0 to 4 inclusive For calls tothe local zone 0 it will be recalled that since sequence switch 700 is set into position 13 the sequence switch 600 is not advanced out. of position 1 and, therefore, no timing or charging is made for either the initial period of conversation or for the overtime periods. For calls to zone ,1 with sequence switch 7 00 in position 14 and zone relays 609 and 610 both non-operated, if no charging for overtime periods is to be made, conductor 634Vwill be connected to the outer right front contact of zone relay 610 and conductor 636 will be connected to the outer right armature of relay 610. When, therefore, the check is made in position 18 of sequence switch 600 at the end of the initial period of conversation to determine if the subscribers are still conversing, the circuit previously traced will be closed and relay 621 will operate. Since,however, zone relay 610 is not operated for a call to zone 1 the previously traced circuit from battery through sequence switch magnet 600, left contact of cam 628, outer left front contact of relay 621, conductor 633, middle upper front contact of relay 302,.conductor 634, front contact of relay 610, conductor 636, the lower right contact of cam 631, the lower right contact of cam 632, conductor 637, the front contact of relay 716 to ground at the lower left contact of cam 720, will be open at the front contact of relay 610 and sequence switch 600 will remain in position 18 until disconnection takes place, and no charge will be registered for the overtime periods of conversation.

If the trafiic requirements are such that a charge should be made for each overtime period onall calls to zone 1 then conductor 634 will be connected over conductor 639 to conductor 636, rather than through front contacts of relay 610 and the previously traced circuit for advancing sequence switch 600 into position'l will be established. From position 1 sequence switch 600 is advanced into position 2 in the manner previously described for a call to zone 5 causing a single operation of the message register 105, following which sequence switch 600 advances into position 3. From position 3, sequence switch 600 is advanced into position 7 over a circuit extending from battery, winding of magnet 600,'upper right contact of cam 617, right back contact of relay 610 to ground over the left contacts of cam 632. Sequence switch 600- is then advanced into position 8 over a circuit extending from battery through the winding of magnet 600, lower right contact of cam 617, conductor 633, middle upperfront contact of relay 302, conductor 634i, conductor 639, conductor 636, lower right contact of cam 631 to ground at the lower left contact of cam 632. In position 8 a circuit is established from battery over conductor 622, the lower contacts of cam 603, conductor 311, winding of relay 305, codnductor 312, right back contact of relay 621, left contacts of cam 620 to ground at the oiiice timing circuit 630. Relay 305 operates in this circuit looking as previously described through the winding of relay 621. Relay 621 operates in this locking circuit as soon as ground is removed at the timing circuit 630, closing a circuit from battery, winding of mag net 600, inner left front contactof relay 621, lower left contacts of cams 631 and 632 to ground. Sequence switch 630 thereupon advances into position. 9, releasing relays 621 and 305. In position 9 relays 621 and 305 again operate, advancing sequence switch 600into position 10. In this manner, se quence switch 600 advances from position to position into. position 18, measuring an overtime period of five minutes. In position 18 a check is again made to determine if the conversation still continues and if so, sequence switch 600 is advanced into position 1 and thence through a further cycle in the manner just described.

For calls to zone 2 with sequence switch 700 is in position 13 and the zone relay 610 operated, when the check is made in position 18 of sequence switch 600 to determine if the subscribers are still conversing at the end of the initial period of conversation the circuit previously traced for advancing sequence switch into position 1 for starting an overtime charging and timing cycle, is closed and sequence switch 600 will be advanced to position 8 in the manner previously described in connection with calls into 

